Ahtanum Creek eroded laterally beyond the limits of its riparian corridor.  Stream discharge increasingly flows along a farm road which parallels the creek through fields for a distance of about 550 feet before returning to the creek.  Low to moderate flood events have eroded the road 2 to 2.5 feet in depth and eroded the stream bank at the point of flow return back to the stream.  Thus, the stream is actively forming an avulsion along the road and once established will provide the most hydraulically efficient path from stream flows possibly becoming the main channel (See Figure 1.)
 

This project would reconstruct the riparian corridor and stream bank by construction of a vegetated timber crib.  The crib was constructed with large woody debris (LWD) with root wads extending into the stream, wood slash was used behind the face of the crib to retain stream gravels placed within the depth of the crib (See Figure 2.)

Figure 2.  Where Ahtanum Creek used to access farming road during high flows.  Bank stabilized to keep creek in original channel.

Three foot diameter boulders was cabled to the top logs of the crib for ballast. Riparian vegetation was placed in the crib and extended beyond the face of the crib above OHW.  The riparian corridor was rehabilitated using vertical log snags to hold LWD placed on the flood plain to restore riparian corridor hydraulic roughness and planting of native riparian vegetation.  An existing side channel was enhanced with slash and overhanging vegetation for off channel rearing habitat. This project was protecting against lateral erosion sourcing fine sediments into the stream and avulsion of the creek along approximately 550 feet of farm road through an adjacent field.

SWP Home  Habitat Home